Digital transmission systems typically carry multiple time division multiplexed channels. For example, the T-1 (or T1) system commonly used in the United States and Canada can handle 24 simultaneous voice conversations (or data equivalents). The European counterpart (E-1 or E1) can carry 31 channels. Although digital telecommunications lines may be used for any digital data, the basic specifications originate from the requirements for digitized voice. Digitization of analog voice requires 8,000 samples per second to satisfy the Nyquist criteria of twice the highest voice frequency of 4,000 Hz. Coding each sample into 8-bits (called octets in the telecommunication industry) results in the fundamental digital voice channel rate of 64 kbps (thousand bits per second). As a result, for T1 and E1 digital telephone circuits, each channel has a bandwidth of 64 kbps, formatted as 8,000 octets per second.
Multiple channels can be concatenated together to form a single higher-rate channel referred to as a fractional T1 (or E1) channel. For example, two channels can be combined to make a single 128 kbps channel. In general, during troubleshooting or performance monitoring, which channels and how many channels are combined to make these fractional channels may not be known. There is a need for automatic determination of how many fractional channels exist on a circuit and which channels are combined into each fractional channel. There is also a need for identification of the type of traffic that is present on each fractional channel.